FR3049847A1 - CUTTING PATTERN OF AN APPARATUS FOR CUTTING A HUMAN OR ANIMAL TISSUE - Google Patents

Abstract

The present invention relates to an apparatus for cutting a human or animal tissue including a device for treating a beam L.A.S.E.R. generated by a femtosecond laser, and disposed downstream of said femtosecond laser, the processing device comprising: - a shaping system (3) for modulating the phase of the beam front L.A.S.E.R. according to a modulation instruction calculated to distribute the energy of the beam L.A.S.E.R. in at least two impact points forming a pattern in its focal plane corresponding to a cutting plane; - an optical scanning scanner (4) arranged downstream of the shaping system to move the pattern in the cutting plane; a plurality of positions in a direction of movement, the pattern being inclined with respect to the direction of movement.

Description

CUTTING PATTERN OF AN APPARATUS FOR CUTTING A HUMAN TISSUE

OR ANIMAL

Technical area

The present invention relates to the technical field of surgical operations performed with femtosecond laser, and more particularly that of ophthalmic surgery for particular applications of cornea cuts, or crystalline lenses. The invention relates to a device for cutting human or animal tissue, such as a cornea, or a lens, by means of a femtosecond laser.

By femtosecond laser is meant a light source capable of emitting a beam L.A.S.E.R. in the form of ultra-short pulses, whose duration is between 1 femtosecond and 100 picoseconds, preferably between 1 and 1000 femtoseconds, in particular of the order of one hundred femtoseconds.

Previous art

It is known from the state of the art to perform surgical operations of the eye by means of a femtosecond laser, such as cutting operations of corneas or lenses.

The femtosecond laser is an instrument capable of cutting the comedic tissue, for example, by focusing a beam L.A.S.E.R. in the stroma of the cornea, and realizing a succession of small adjacent cavitation bubbles, which then forms a cutting line.

More precisely, during the focusing of the beam L.A.S.E.R. in the cornea, a plasma is generated by nonlinear ionization when the intensity of the laser exceeds a threshold value, called optical breakdown threshold. A cavitation bubble then forms, causing a very localized disruption of the surrounding tissues. Thus, the volume actually ablated by the laser is very small compared to the disrupted area.

The area cut by the laser at each pulse is very small, of the order of one micron or ten micron depending on the power and focus of the beam. Thus, a corneal lamellar cut can only be obtained by making a series of adjacent impacts on the entire surface of the area to be cut.

The displacement of the beam can then be achieved by a scanning device, consisting of controllable galvanometric mirrors, and / or platens allowing the displacement of optical elements, such as mirrors or lenses. This scanning device makes it possible to move the beam along a path back and forth along a succession of segments forming a path of movement of the beam.

To cut a cornea on a surface of Imm ^, it is necessary to realize about 20000 impacts very close to each other. Today these impacts are achieved one by one at an average speed of 300000 impacts / second. To cut a cornea over an area of about 6 mm, taking into account the times during which the laser stops generating end-of-segment pulses to allow the mirrors to be positioned on the next segment, it takes on average 15 seconds. The surgical cutting operation is therefore slow.

To optimize the cutting time, it is known to increase the frequency of the laser. However, increasing the frequency also implies an increase in the speed of displacement of the beam, by means of adapted plates or scanners. It is also known to increase the spacing between the impacts of the laser on the tissue to be cut, but generally to the detriment of the quality of the cut.

Most femtosecond lasers for corneal cutting thus use high working frequencies, especially greater than 100 kHz, associated with beam displacement systems combining scanners and displacement plates, which strike the total cost of the installation, and therefore the invoiced surgical operation.

To remedy this problem of speed of cutting L.A.S.E.R., it is also known to use galvanometric mirrors to increase the rate, speed, and deflection path of the beam L.A.S.E.R.

However, this technique is not entirely satisfactory in terms of results.

Another solution to reduce the cutting time is to generate several cavitation bubbles simultaneously. Simultaneously generating "n" cavitation bubbles makes it possible to reduce the total duration of the cutting by a factor "n". The reduction of a beam into several beams, with the aim of accelerating the procedure, has already been described but still by means of purely optical solutions, either by diffraction or by multiple reflections. The result was never clinically exploitable, mainly because the different beams were not of homogeneous size.

An object of the present invention is to provide a cutting apparatus for overcoming at least one of the aforementioned drawbacks.

For this purpose the invention provides an apparatus for cutting a human or animal tissue, such as a cornea, or a lens, said apparatus including a device for treating a beam L.A.S.E.R. generated by a femtosecond laser, and disposed downstream of said femtosecond laser, the processing device comprising: - a shaping system positioned on the path of said beam, for modulating the phase of the beam front L.A.S.E.R. so as to obtain a beam L.A.S.E.R. phase modulated according to a modulation instruction calculated to distribute the energy of the beam L.A.S.E.R. at least two impact points forming a pattern in its focal plane corresponding to a cutting plane, - an optical scanning scanner arranged downstream of the shaping system to move the pattern in the cutting plane into a plurality of positions in a direction of movement, characterized in that the pattern is inclined with respect to the direction of movement so that at least two pattern impact points are spaced a non-zero distance along a first axis parallel to the direction of displacement on the one hand, and a non-zero distance along a second axis perpendicular to the direction of movement on the other hand.

In the context of the present invention, the term "point of impact" is intended to mean a zone of the beam L.A.S.E.R. included in its focal plane in which the intensity of said beam L.A.S.E.R. is sufficient to generate a cavitation bubble in a tissue.

In the context of the present invention, the term "adjacent points of impact" means two impact points arranged facing each other and not separated by another point of impact. "Neighboring impact points" means two points in a group of adjacent points between which the distance is minimal.

In the context of the present invention, the term "motif" refers to a plurality of points of impact L.A.S.E.R. generated simultaneously in a focusing plane of a beam L.A.S.E.R. shaped - that is, modulated in phase to distribute its energy in several distinct spots in the plane of focus corresponding to the cutting plane of the device

Thus, the invention makes it possible to modify the intensity profile of the beam L.A.S.E.R. in the plane of the cut, in a way to improve the quality or the speed of cutting according to the chosen profile. This change in intensity profile is obtained by modulating the phase of the beam L.A.S.E.R.

Optical phase modulation is achieved by means of a phase mask. The energy of the beam L.A.S.E.R. incident is retained after modulation, and beam shaping is performed by acting on its wavefront. The phase of an electromagnetic wave represents the instantaneous situation of the amplitude of an electromagnetic wave. The phase depends on time as well as space. In the case of the spatial shaping of a L.A.S.E.R beam, only the variations in phase space are considered.

The wavefront is defined as the area of the points of a beam having an equivalent phase (i.e. the area consisting of the points whose travel times from the source having emitted the beam are equal). The modification of the spatial phase of a beam thus passes through the modification of its wavefront.

This technique makes it possible to perform the cutting operation in a faster and more efficient manner because it implements several spots L.A.S.E.R. each making a cut and according to a controlled profile.

Preferred but non-limiting aspects of the cutting apparatus are as follows: the pattern may comprise at least two adjacent (including three) adjacent impact points extending along a line of the pattern, the angle between said pattern line of the pattern and the direction of movement being between 10 and 80 °, preferably between 15 ° and 40 °, and even more preferably between 19 ° and 30 °; the pattern may comprise a first set of at least two (including three) impact points arranged along a first line of the pattern, and a second set of at least two (including three) other impact points arranged along a second line of the pattern parallel to the first line; the pattern may further comprise at least one other set of impact points arranged along at least one other line of the pattern, parallel to the first and second lines; the impact points of the second set may be offset by a non-zero distance with respect to the points of impact of the first set; each point of impact of the second set may be aligned with a respective point of impact of the first set along a line perpendicular to the direction of movement; the distance between two adjacent impact points of the pattern may be greater than 5 μm, preferably greater than 10 μm and even more preferably between 10 and 15 μm; - The pattern can be inscribed in a surface whose ratio between the length and width is between 1 and 4, preferably between 1 and 2, and even more preferably between 1 and 1.5; - The pattern may include a central point of impact positioned at the center of the pattern.

BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limitative, with reference to the appended figures, in which: FIG. 1 is a schematic representation an assembly including the cutting apparatus according to the invention; FIG. 2 illustrates an intensity distribution of a beam L.A.S.E.R. in its focal plane; Figure 3 illustrates a path of movement of a cutting pattern; Figure 4 illustrates cutting planes of a volume of tissue to be destroyed; Figures 5 to 9, 11 to 18, and 20 to 22, 24 and 28 illustrate different examples of cutting pattern, Figures 10, 19, 23 and 25 to 27 illustrate cavitation bubble matrices.

DETAILED DESCRIPTION OF THE INVENTION The invention relates to an apparatus for cutting a human tissue by means of a femtosecond laser. In the remainder of the description, the invention will be described, by way of example, for cutting a cornea of a human or animal eye. 1. Cutting apparatus

Referring to Figure 1, there is illustrated an embodiment of the cutting apparatus according to the invention. This can be arranged between a femtosecond laser 1 and a target to be treated 2.

The femtosecond laser 1 is able to emit a beam L.A.S.E.R. in the form of pulses. As an example, the laser 1 emits a light of 1030 nm wavelength, in the form of pulses of 400 femtoseconds. The laser 1 has a power of 20W and a frequency of 500 kHz.

The target 2 is for example a human or animal tissue to be cut such as a cornea or a lens. The cutting apparatus comprises: - a shaping system 3 positioned on the path of the beam L.A.S.E.R. 11 from the femtosecond laser 1, - a scanning optical scanner 4 downstream of the shaping system 3, - an optical focusing system 5 downstream of the scanning optical scanner 4. The cutting apparatus also comprises a scanning unit 4. control 6 for controlling the shaping system 3, the scanning optical scanner 4 and the optical focusing system 5.

The shaping system 3 makes it possible to modulate the phase of the beam L.A.S.E.R. 11 from the femtosecond laser 1 to distribute the energy of the beam L.A.S.E.R. in a plurality of impact points in its focal plane, this plurality of impact points defining a pattern

The scanning optical scanner 4 makes it possible to orient the beam L.A.S.E.R. modulated in phase 31 from the shaping system 3 to move the cutting pattern along a predetermined path of travel by the user in the plane of focus 21.

The optical focusing system 5 makes it possible to move the plane of focus 21 corresponding to the cutting plane of the beam L.A.S.E.R. modulated and deflected 4L

Thus, the shaping system 3 makes it possible to simultaneously generate several impact points defining a pattern, the scanning optical scanner 4 makes it possible to move this pattern in the focusing plane 21, and the focusing optical system 5 makes it possible to move the plane of focus 21 in depth so as to generate cuts in successive planes defining a volume.

The various elements constituting the cutting apparatus will now be described in more detail with reference to the figures. 2. Elements of the cutting apparatus 2.1.Forming system

The spatial shaping system 3 of the beam L.A.S.E.R. allows to vary the beam surface of the beam L.A.S.E.R. to obtain points of impact separated from each other in the focal plane. More precisely, the shaping system 3 makes it possible to modulate the phase of the beam L.A.S.E.R. 11 from the femtosecond laser 1 to form intensity peaks in the focal plane of the beam, each intensity peak producing a respective point of impact in the focal plane corresponding to the cutting plane. The shaping system 3 is, according to the illustrated embodiment, a liquid crystal light spatial modulator, known by the acronym SLM, of the acronym "Spatial Light Modulator".

The SLM makes it possible to modulate the final energy distribution of the L.A.S.E.R. beam, in particular in the focal plane 21 corresponding to the cutting plane of the fabric 2. More specifically, the SLM is adapted to modify the spatial profile of the wavefront of the L.A.S.E.R. beam. primary 11 from the femtosecond laser 1 to distribute the energy of the beam L.A.S.E.R. in different focusing spots in the focusing plane.

Phase modulation of the wavefront can be seen as a two-dimensional interference phenomenon. Each portion of the beam L.A.S.E.R. initial source from the source is delayed or advanced relative to the initial wavefront so that each of these portions is redirected so as to achieve constructive interference at N distinct points in the focal plane of a lens. This redistribution of energy at a plurality of impact points takes place in only one plane (i.e., the focus plane) and not all along the propagation path of the beam L.A.S.E.R. module. Thus, the observation of the beam L.A.S.E.R. modulated before or after the plane of focus does not identify a redistribution of energy in a plurality of different points of impact, because of this phenomenon that can be likened to constructive interference (which takes place only in one plane and not throughout the propagation as in the case of the separation of an initial LASER beam into a plurality of secondary LASER beams).

To better understand this phase modulation phenomenon of the wavefront, FIG. 2 schematically illustrates intensity profiles 32a-32e obtained for three examples of distinct optical assemblies. As shown in FIG. 2, a beam L.A.S.E.R. 11 emitted by a laser source 1 produces a gaussian intensity peak 32a at an impact point 33a in a focusing plane 21. The insertion of a beam splitter 7 between the source 1 and the focusing plane 21 induces the generation of a plurality of LASER beams 71, each beam L.A.S.E.R. secondary 71 producing a respective point of impact 33b, 33c in the focal plane 21 beams L.A.S.E.R. 71. Finally, the insertion between the source 1 and the focusing plane 21 of a SLM 3 programmed using a phase mask forming a modulation instruction induces the modulation of the phase of the wavefront of the LASER beam 11 from the source 1. The beam L.A.S.E.R. 31 whose wavefront phase has been modulated allows to induce the production of several peaks of intensity 33d, 33e separated spatially in the focal plane 21 of the LASER beam, each peak 32d, 32e corresponding to a point of impact 33d, 33e respectively making a cut. The modulation technique of the wavefront phase makes it possible to generate several simultaneous cavitation bubbles without reducing the beam L.A.S.E.R. initial produced by the femtosecond laser 1.

The SLM is a device consisting of a controlled orientation liquid crystal layer for dynamically shaping the wavefront, and thus the beam phase L.A.S.E.R. The liquid crystal layer of an SLM is organized as a grid (or matrix) of pixels. The optical thickness of each pixel is electrically controlled by orientation of the liquid crystal molecules belonging to the surface corresponding to the pixel. SLM (9) exploits the principle of anisotropy of liquid crystals, that is to say the modification of the index of liquid crystals, as a function of their spatial orientation. The orientation of the liquid crystals can be carried out using an electric field. Thus, the modification of the index of the liquid crystals modifies the wavefront of the beam L.A.S.E.R. (4). In a known manner, the SLM implements a phase mask, that is to say a map determining how the phase of the beam must be modified to obtain a given amplitude distribution in its plane of focus. The phase mask is a two-dimensional image with each point associated with a respective pixel of the SLM. This phase mask makes it possible to control the index of each liquid crystal of the SLM by converting the value associated with each point of the mask - represented in grayscale between 0 and 255 (hence from black to white) - into a control value - represented in a phase between 0 and 2π. Thus, the phase mask is a modulation setpoint displayed on the SLM for reflecting in reflection an unequal spatial phase shift of the beam L.A.S.E.R. (4) illuminating the SLM. Of course, those skilled in the art will appreciate that the gray level range may vary depending on the SLM model used. For example, in some cases, the gray level range may be between 0 and 220. The phase mask is generally calculated by an iterative algorithm based on the Fourier transform, or on various optimization algorithms, such as algorithms genetic, or simulated annealing. Different phase masks can be applied to the SLMs depending on the number and position of the desired points of impact in the focal plane of the beam L.A.S.E.R. In all cases, one skilled in the art can calculate a value at each point of the phase mask to distribute the energy of the beam L.A.S.E.R. in different focusing spots in the focal plane.

The SLM therefore makes it possible, from a beam L.A.S.E.R. Gaussian generating a single point of impact, and by means of the phase mask, to distribute its energy by phase modulation so as to simultaneously generate several points of impact in its plane of focus from a single beam L.A.S.E.R. phase-modulated (a single beam upstream and downstream of the SLM).

In addition to a decrease in the cutting time of the cornea, the beam phase modulation technique L.A.S.E.R. allows other improvements, such as better surface quality after cutting or a reduction in endothelial mortality. The different points of impact of the pattern may, for example, be evenly spaced on the two dimensions of the focal plane of the L.A.S.E.R. beam, so as to form a grid of spots L.A.S.E.R.

Thus, the shaping system 3 makes it possible to perform a surgical cutting operation in a fast and efficient manner. The SLM makes it possible to dynamically shape the beam front of the beam L.A.S.E.R. since it is numerically configurable. This modulation makes it possible to shape the beam L.A.S.E.R. in a dynamic and reconfigurable way.

The SLM can be configured to shape the beam front of the beam L.A.S.E.R. in any other way. For example, each impact point may have any geometrical shape, other than circular (for example in an ellipse, etc.). This may have certain advantages depending on the application considered, such as an increase in the speed and / or the quality of the cut. 2.2. Optical Halavase Scanner

The scanning optical scanner 4 makes it possible to deflect the beam L.A.S.E.R. modulated in phase 31 so as to move the pattern 8 at a plurality of positions 43a-43c in the plane of focus 21 corresponding to the cutting plane.

The scanning optical scanner 4 comprises; an inlet orifice for receiving the beam L.A.S.E.R. modulated in phase 31 from the forming unit 3, - one (or more) optical mirror (s) pivoting about at least two axes to deflect the beam L.A.S.E.R. modulated in phase 31, and - an output port for sending the beam L.A.S.E.R. modulated deflected 41 to the optical focusing system 5.

The optical scanner 4 used is for example an IntelliScan scanning head ΠΙ from SCANLAB AG.

The inlet and outlet ports of such an optical scanner 4 have a diameter of the order of 10 to 20 millimeters, and achievable scanning speeds are of the order of Im / s to 10 m / s.

The mirror (s) is (are) connected (s) to (or) motor (s) to allow their pivoting. This motor (s) for pivoting the mirror (s) is (are) advantageously controlled by the unit of the control unit 6 which will be described in more detail below. The control unit 6 is programmed to drive the scanning optical scanner 4 so as to move the pattern 8 along a path of movement 42 contained in the plane of focus 21. In some embodiments, the path of movement 42 comprises a plurality of cutting segments 42a-42c. The displacement path 42 may advantageously have a slot shape. In this case, if the optical scanner 4 starts a first cutting segment 42a from the left, it will start the second cutting segment 42b from the right, then the third cutting segment 42c from the left, then the next segment from the right and so on along the entire path of movement 42 of the pattern 8. This speeds up the cutting of the fabric avoiding the need for the optical scanner 4 to reposition the pattern 8 at the beginning of each successive cutting segment 42a-42c.

To further accelerate the cutting operation in the plane of focus 21, the displacement path 42 may advantageously have a spiral shape. This makes it possible to keep the scanning speed of the optical scanner 4 constant throughout the cutting plane. Indeed, in the case of a toothed path 42, the optical scanner 4 must stop at the end of each cutting segment 42a to move on the next cutting segment 42b, which consumes some time.

The scanning of the beam is of great importance for the result of the cut obtained. Indeed, the scanning speed used, as well as the scanning pitch, are parameters influencing the quality of the cut.

Preferably, the scanning pitch - corresponding to the distance "dist" between two adjacent positions 43a, 43b of the pattern 8 along a segment of the displacement path 42 - is chosen to be greater than or equal to the diameter of a dot of impact 81 of the pattern 8. This makes it possible to limit the risks of superposition of the points of impact during successive shots.

Also, when the travel path 42 has a square shape, the distance "ec" between two adjacent segments 42a, 42b of the travel path 42 is preferably greater than the dimension of the pattern 8 along a perpendicular to its direction of travel. . This also makes it possible to limit the risks of superposition of the points of impact 81 during successive shots.

Finally, in order to limit the duration of the cutting operation in the cutting plane, while guaranteeing a certain quality of the cut, the distance between two adjacent segments 42a, 42b of the displacement path 42 can be chosen equal to a maximum ( and preferably lower) of 3N times the diameter of an impact point 81, where N is the number of impact points of the pattern 8.

In one embodiment, the cutting apparatus further comprises a Dove prism. This is advantageously positioned between the shaping system 3 and the scanning optical scanner 4. The prism of Dove makes it possible to implement a rotation of the pattern 8 which may be useful in certain applications or to limit the size of the priming area of each cutting segment 42a-42c.

Advantageously, the control unit 6 can be programmed to activate the femtosecond laser 1 when the scanning speed of the optical scanner 4 is greater than a threshold value.

This makes it possible to synchronize the emission of the beam L.A.S.E.R. 11 with scanning of the scanning optical scanner 4. More precisely, the control unit 6 activates the femtosecond laser 1 when the rotation speed of the mirror (s) of the optical scanner 4 is constant. This makes it possible to improve the quality of cutting by performing a homogeneous surfacing of the cutting plane. 2.3. Focusing optical system

The optical focusing system 5 makes it possible to move the focusing plane 21 of the beam L.A.S.E.R. modulated and deflected 41 in a cutting plane of tissue 2 desired by the user.

The optical focusing system 5 comprises: an input port for receiving the beam L.A.S.E.R. phase modulated and deflected from the scanning optical scanner, - one (or more) motorized lens (s) to allow its (their) displacement in translation along the optical path of the beam L.A.S.E.R. phase modulated and deflected, and - an output port for sending the beam L.A.S.E.R. focused towards the tissue to be treated. The lens (or lenses) used with the optical focusing system 5 may be f-theta lenses or telecentric lenses. The f-theta and telecentric lenses make it possible to obtain a focusing plane, especially the XY field, contrary to the standard lenses for which it is curved. This ensures a constant focused beam size across the field. For f-theta lenses, the position of the beam is directly proportional to the angle applied by the scanner while the beam is still normal to the sample for telecentric lenses. The control unit 6 is programmed to control the displacement of the lens (s) of the optical focusing system 5 along an optical path of the beam L.A.S.E.R. so as to move the focusing plane 21 in at least three respective cutting planes 22a-22e so as to form a stack of cutting planes of the fabric 2. This allows a cut in a volume 23, for example in the part of a refractive surgery. The control unit 6 is able to control the displacement of the optical focusing system 5 to move the plane of focus 21 between a first extreme position 22a and a second extreme position 22e, in this order. Advantageously, the second extreme position 22e is closer to the femtosecond laser 1 than the first extreme position 22a.

Thus, the cutting planes 22a-22e are formed starting with the deepest cutting plane 22a in the fabric and stacking the successive cutting planes to the most superficial cutting plane 22e in the fabric 2. It avoids thus the problems associated with the penetration of the LASER beam 2. In fact, cavitation bubbles form an opaque bubble barrier (known as "OBL", the acronym for "Opaque Bubble Layer") preventing the propagation of energy from the beam LASER under these. It is therefore preferable to start by generating the deepest cavitation bubbles in priority in order to improve the efficiency of the cutting apparatus.

Preferably, the length of the optical path between the shaping system 3 and the optical focusing system 5 is less than 2 meters, and even more preferably less than 1 meter. This makes it possible to limit power losses due to energy dispersed in the optical path. Indeed the greater the distance between the shaping system 3 and the optical focusing system 5, the greater the loss of power on the path is important.

Advantageously, the control unit 6 can be programmed to vary the shape of the pattern 8 between two cutting planes 22a-22b (or 22b-22c, or 22c-22d, or 22d-22e) successive. Indeed, when cutting into a volume 23, it may be preferable to increase the precision of the cut in the peripheral cutting planes 22a, 22e and to increase the cutting speed in the intermediate cutting planes 22b, 22c 22d located between the peripheral cutting planes 22a, 22e. For example, in the case of cutting a volume 23 composed of a stack of five cutting planes 22a-22e, the control unit 6 can drive the shaping system 3 by transmitting: - a first mask phase corresponding to a first pattern making it possible to increase the accuracy of the cut when the plane of focus corresponds to the first and fifth cutting planes 22a and 22e; - a second phase mask when the plane of focus corresponds to the second, third and fourth cutting plane 22b-22d.

Similarly, the control unit 6 can be programmed to vary the pitch "dist" of the scanning optical scanner 4 and / or the shape of the cut area (by changing the path of movement of the pattern) between two cutting planes respectively. This also makes it possible to increase the accuracy of the cutting or the cutting speed in one cutting plane to another.

Finally, the control unit 6 can be programmed to control the scanning optical scanner 4 so as to vary the area cut in the plane of focus 21 between two successive cutting planes 22d, 22e. This makes it possible to vary the shape of the volume 23 finally cut according to the intended application.

Preferably, the distance between two successive cutting planes is between 2 μm and 500 μm, and in particular: between 2 and 20 μm to process a volume requiring high precision, for example in refractive surgery, preferably with a spacing between and lOpm, or between 20 and 500pm to treat a volume that does not require high accuracy, such as for example to destroy the central portion of a Uni-crystal nucleus, with preferably a spacing between 50 and 200pm.

Of course, this distance may vary in a volume 23 composed of a stack of cutting planes 22a-22e. 2.4. Control unit

As indicated above, the control unit 6 makes it possible to control the various elements constituting the cutting apparatus, namely the femtosecond laser 1, the shaping system 3, the scanning optical scanner 4 and the optical focusing system 5. The control unit 6 is connected to these different elements via one (or more) communication buses allowing: - the transmission of control signals such as • the phase mask to the shaping system , • the femtosecond laser activation signal, • the scan speed at the scanning optical scanner, • the position of the scanning optical scanner along the path of movement, • the depth of cut at the optical focusing system. the reception of measurement data from the various elements of the system such as the scanning speed reached by the optical scanner, or the position of the optical focusing system, etc. The control unit 6 may be composed of one (or more) work station (s), and / or one (or more) computer (s) or may be of any other type known to the person in charge. job. The control unit 6 may for example comprise a mobile phone, an electronic tablet (such as an IP AD®), a personal assistant (or "PDA", acronym of the expression "Personal Digital Assistant") etc. In all cases, the control unit 6 comprises a processor programmed to enable control of the femtosecond laser 1, the shaping system 3, the scanning optical scanner 4, the focusing optical system 5, etc. 2.5.Motif

The reconfigurable modulation of the beam front L.A.S.E.R. allows to generate multiple simultaneous impact points 81 each having a size and a controlled position in the plane of focus 21.

These different points of impact 81 form a pattern 8 in the focal plane 21 of the beam L.A.S.E.R. module.

The number of impact points 81 of the pattern 8 decreases by as many times the time required for the surgical cutting operation.

However, the size of the pattern 8, the number of impact points 81 that it comprises and their respective positions with respect to the direction of displacement are technical characteristics chosen judiciously to meet the technical constraints associated with the cutting of fabric, as it will emerge in the following. 2.5.1. Constraints and chosen solutions 2.5.1.1.Maximum number of points of impact per reason

In order to accelerate the cutting of the fabric 2, it is preferable to have a pattern 8 including a maximum number of impact points 81. In current ophthalmic laser systems, the energy per pulse and per spot necessary for cutting comedian is around 1 pJ. Thus, with a femtosecond laser - such as a Satsuma laser source (marketed by Amplitude System) - providing a power of 20W at a rate of 500kHz, or a maximum of 40pJ / pulse energy, it is theoretically possible to create a pattern 8 composed of 40 identical impact points.

However, in any laser system, losses occur along the optical path. Thus, in a prototype tested by the Applicant, the power reaching the cornea was only 12W for shaping six impact points 81 of overall size (30 pm * 22 pm). The focused beam diameter was 8pm in diameter, compared to around 4pm maximum for current ophthalmic lasers. In the context of a prototype tested by the Applicant, a 4 times higher energy per spot was required compared to current ophthalmic lasers, 4pJ. So for this prototype, it was chosen to use a pattern composed of six points of impact 81 (at most). Of course, if the power of the femtosecond laser 1 is greater, the pattern 8 may comprise a number of impact points 81 greater than six. 2.5.1.2.Distribution of impact points in the pattern

The six impact points 81 of the pattern 8 can be distributed according to different configurations.

For example, the six impact points 81 may be distributed along a single line. The total length of the pattern 8 is then equal to the sum between the diameter of an impact point 81 and the center-to-center distance between the extreme impact points 81 of the pattern 8. The width of the pattern 8 is itself equal to the diameter of a point of impact 81.

As indicated previously, the shaping of the beam L.A.S.E.R. causes a loss of power, due to energy scattered on the optical path. The overall size of the shaping (and thus the size of the pattern 8) is one of the factors influencing this energy loss.

The larger the size (in length or width) of pattern 8 is, the greater the power loss. A distribution of six points of impact 81 on a single line thus induces a significant loss of power. As a guide: - A pattern 8 of size 30 pm*22pm comprising six impact points 81 causes a loss of power of about 10%, while - a pattern 8 of size 84 pm*20pm comprising five points of impact 81 causes a power loss of about 25%.

Thus, for a given number of impact points 81, the "compact" patterns (ratio of length and width sizes close to 1) result in a lower energy loss. This is why the impact points 81 of the pattern 8 are preferably included in a surface whose ratio between the length and the width is between 1 and 4, preferably between 1 and 2, and even more preferably between 1 and 1.5. .

For example, the six impact points 81a-81f of the pattern may be distributed on first and second parallel lines 82, 83: the first line 82 passing through three impact points 81a-81c forming a first triplet, and the second line 83 passing through three other points of impact 81d-81f forming a second triplet distinct from the first triplet.

A pattern corresponding to this distribution is illustrated in FIG. 5. Advantageously, the points of impact 81a-81f of the pattern can be shifted from one line to another in the direction of displacement D. More precisely, the points impact 81a-81c of the first triplet can be shifted by a non-zero distance (according to the direction of displacement D) with respect to the points of impact 81d-81f of the second triplet. This makes it possible to avoid the superposition of cavitation bubbles in the cutting plane during the displacement of the pattern 8 by the scanning optical scanner 4. 2.5.1.3.Distance minimal between points of impact of the pattern

In addition to the distribution of the points of impact 81 of the pattern 8, another parameter of the pattern concerns the distance between the adjacent points of impact.

This distance is defined by constraints related to the formatting system.

During the shaping operation of the beam L.A.S.E.R. from the femtosecond laser, the "too close" impact points interfere with each other due to the spatial coherence of the source. These interferences degrade the shape of the points of impact and make it impossible to control the level of laser intensity on each point of impact. It is therefore preferable that the distance between the adjacent impact points of the pattern is sufficient to limit this phenomenon of interference between points of impact too close.

This "sufficient distance" depends on the focus of the beam. The more focused the beam, the lower the distance. Conversely, the less the beam is focused, the more this distance will be important.

Taking into account the working distance constraints related to surgical applications of the anterior segment of the eye, the reproducibility of the shaping as well as the aberrations of the optical system degrading the spatial coherence of the beam, the separation limit of two spots is around 10pm. This is why the "sufficient distance" from center to center between two adjacent impact points is greater than 5pm, preferably greater than 10pm and even more preferably between 10pm and 20pm, especially between 10pm and 15pm. 2.5.1.4.Orientation of the reason in relation to the direction of travel

The basic shape illustrated in Figure 5 can be oriented in different ways in the mesh. The most obvious orientation of this basic form for those skilled in the art is illustrated in Figure 6. This orientation consists of moving the pattern in a direction of movement D perpendicular to the two lines 82, 83 defined by the first and second triplets of 81a-81c and 81d-81f impact points

However, several limitations related to the shaping system and the moving direction of the pattern prevent the use of such orientation.

As described above, the distance between two adjacent impact points 81a, 81b of the pattern is preferably greater than 10 μm. By moving the pattern in a direction of movement perpendicular to the two lines 82, 83 defined by the first and second triplets of impact points 81a-81c, 81d-81f, the distance between the cavitation bubbles generated on adjacent segments 42a, 42b parallel to the direction of movement of the pattern will be of the order of 15 pm.

However, a "classical" distance between adjacent cavitation bubbles for cutting a cornea is of the order of 2 pm to 7 pm, in particular equal to 5 pm.

It is therefore necessary to "tilt" the pattern 8 so that the neighboring cavitation bubbles generated on segments 42a, 42b adjacent to the direction of movement D of the pattern 8 are spaced a distance substantially equal to 5pm at the direction of movement.

Note that on the same segment 42a, the distance of 5pm between two adjacent cavitation bubbles can be obtained by adjusting the displacement step of the scanning optical scanner 4. 2.5.2. Examples of reasons

Referring to Figures 7 to 9, there is illustrated various examples of pattern usable with the cutting apparatus according to the invention.

In the embodiment illustrated in FIG. 7, the pattern comprises three impact points 81a-81c extending along a line 82 of the pattern 8. The impact points are spaced apart by a distance "d" in the direction of movement D. The line of the pattern is inclined by an angle "a" with respect to the moving direction D of the scanning optical scanner 4 so that the cavitation bubbles along a line perpendicular to the direction of movement D are spaced apart by a distance "e" in the cutting plane. We then have the following relation between the different distances "d" and "e", and the angle of inclination "a"

Preferably, the angle of inclination "a" of the pattern is between 10 ° and 80 °. In the embodiment illustrated in FIG. 8, the pattern comprises four impact points 81a-81d extending along two parallel lines 82, 83 of the pattern 8: a first pair of impact points 81a, 81b extends along a first line 82 of the pattern, - A second pair of impact points 81c, 81d extends along a second line 83 of the pattern.

This pattern has a square shape inclined at an angle of inclination "a" with respect to the direction of movement of the scanning optical scanner. We have the following relation:

With: "a" the angle of inclination of each line of the pattern relative to the direction of movement, "d" corresponding to the distance between two adjacent points of impact, and "e" corresponding to the distance between two points impactors adjacent in a direction perpendicular to the direction of movement of the pattern.

In the embodiment illustrated in FIG. 9, the pattern comprises six points of impact 81a-81f extending along two lines parallel to the pattern 8: a first triplet of points of impact extends along a first line of the pattern, - A second triplet of points of impact extends along a second line of the pattern

This pattern has a rectangle shape inclined at an angle of inclination "a" with respect to the direction of movement of the scanning optical scanner. We have the following relation:

With: - "a" the angle of inclination of each line of the pattern with respect to the direction of movement, "d" being the distance between two adjacent points of impact, and "e" corresponding to the distance between two adjacent impact points in a direction perpendicular to the direction of movement of the pattern 2.5.5. Theory of Pattern Determination

In the following, we will describe an approach implemented by the Applicant to determine possible shapes of impact point patterns to ultimately obtain a cavitation bubble arrangement composed of a repetitive regular matrix: - either in square, - in an equilateral triangle, while respecting the minimum spacing between adjacent impact points to limit the interference phenomenon described above.

There is a variety of possible patterns to obtain by projection during their displacement a homogeneous and repetitive matrix of cavitation bubbles 5pm apart from each other, over the entire surface treated. But there is also an "ideal" matrix whose points of impact are distant enough to avoid interference, and close enough so that the total surface of the pattern is small and fits in a restricted field, which is preferable because the limited size of optics and mirrors in the path of the LASER beam

We proceeded simply by observing an arrangement of spots, either with a square matrix or with an equilateral triangle matrix, and we determined the possible reasons for obtaining this arrangement, once the motive set in motion by the optical scanning scanner. 2.5.3.1.Research for a pattern to obtain an equilateral triangle matrix cavitation bubble arrangement

In FIG. 10 illustrating a cut-off plane including a plurality of cavitation bubbles 100, an equilateral triangle-like bubble arrangement 101 can be observed. The observation leads us to identify several possible motifs, which are part of this matrix. as shown in FIGS. 1a to 1c.

In practice none of the three matrices presented above is usable. Indeed, if the distance separating 2 bubbles from the cut surface is D, or 5pm, it is also necessary to avoid interference that the minimum distance between 2 impact points of the pattern is equal to lOpm or at least 2D.

However, in the three examples of patterns illustrated in FIGS. 1a to 1a, there are always at least two points of impact of the pattern that are too close to one another (distance = D * (Cos (30 °) * 2) = 1 , 73 * D. Let for D = 5 pm a distance of 8.65 pm (cf figure 12).

These observations thus lead us to define a pattern whose all the points of impact are at least distant from each other of 2 * D and which makes it possible to obtain the arrangement in equilateral triangle pattern.

A first example of a pattern is illustrated in FIGS. 13 to 15, in which all the points are distant from each other by at least 2 * D, ie for the distances A and B if D = 5pm: • A = D * cos ( 30 °) * 4 = 17 μια

On the other hand, the distance between the two most spaced points of the matrix is C = V (4,5fl) 2 -I- (cos (30 °) * 5f1) 2 = 31,22 pm Finally, on this matrix, a precise angulation (cf figure 15) makes it possible to reproduce the regular pattern in equilateral triangle, and the angles with respect to the horizontal and the vertical are: A = B ^ 005 (30 ^^ 4

at 19, r P 16.1 *

A second example of a pattern is illustrated in FIGS. 16 to 18, in which all the points are distant from each other by at least 2 * D, ie for the distances A if D = 5pm:

On the other hand, the distance between the two most distant points of the matrix is

Finally, on this ground, a precise angulation makes it possible to reproduce the matrix in equilateral triangle, and the angles with respect to the horizontal and the vertical are:

a = 19, r β = 15, r

From the foregoing, we have just demonstrated that two different patterns could be used to obtain, after being set in motion, an arrangement of regular bubbles arranged according to an equilateral triangle matrix.

The choice between the first or second pattern would rather favor the first, because the maximum spacing between the 2 most distant points is 31.22 pm instead of 35pm, so a more compact form.

Another advantage of these reasons is that the number of points can be increased to more than 6 (2 X 3 points) by adding new rows of points, respecting the same distances and angulations and moving to patterns of 9 ( 3 X 3) or 12 points (3 X 4) or more. 2.5.3.2.Research for a pattern to obtain a square matrix matrix cavitation bubble

In FIG. 19 illustrating a cut-off plane including a plurality of cavitation bubbles 100, we can observe a matrix-like square bubble arrangement 101. The observation leads us to identify a possible pattern, which fits into this matrix, and which respects the minimum spacing between 2 points equal to 2 times the distance D: •

• E = 3D = 15 μια. On the other hand, the distance between the two most distant points of the pattern is:

Finally, on this matrix, a precise angulation makes it possible to reproduce the regular pattern in square, and the angle with respect to the horizontal is a = 26.56 °. 2.5.3.3. Special case of intertwined motifs

We have described the principle of reuse of laser spot patterns to obtain a homogeneous arrangement of cavitation bubbles in the treated tissue. These patterns have a particular arrangement of laser spots, whose arrangement relative to each other, and the distances that separate them, allow to respect the constraints described above, and in particular the minimum distance between each spot to avoid interference, and the maximum distance between each point of impact to obtain a satisfactory tissue cutting quality. The patterns presented so far, all have the particularity to allow when a movement is applied to them by the scan printed by the scanner, to cover uniformly and evenly a surface of equidistant cavitation bubbles, without leaving untreated areas . At the end of a segment having a regular arrangement of impact points, as shown in FIG. 23, the scanner controls the displacement of the matrix by a step 106 equal to the distance between the most distant strike rows. 104, plus the distance between two contiguous lines 105.

A variant of the pattern shown in FIG. 24 makes it possible to imagine leaving an untreated zone ZNT as shown in FIG. 25, this zone ZNT being able to be processed by the following scanning with an arrangement of intertwined impact points. For this, the step printed by the scanner between two successive segments is not constant and will be one time out of two equal to twice the distance between two rows of contiguous impacts 107, and one time out of two equal to the distance between the rows the farthest impacts 108, plus the distance between two adjacent lines 105. 2.5.3.4. Special case of a central point of impact pattern

Referring to Figure 28, there is illustrated another example of a pattern that can be used to cut a fabric. This pattern comprises a plurality (i.e., at least three) of peripheral impact points 81P, and a central impact point 81B positioned at the centroid of the pattern. In particular in the example illustrated in Figure 28, at the intersection between diagonal axes passing through opposite peripheral impact points.

The presence of this central point of impact makes it possible to take advantage of the phenomena of generation of an energy at the center of the pattern (a phenomenon known under the name "zero order"). Indeed, during the phase modulation of the beam L.A.S.E.R. 11 with the shaping system 3, part of the beam L.A.S.E.R. from the femtosecond laser is not modulated (because of the space between the liquid crystal pixels of the SLM). This part of the beam L.A.S.E.R. unmodulated can induce the generation of a peak of energy forming in the center of the SLM.

When the pattern does not include a point of impact at this center of gravity, it is necessary to limit this peak of zero order energy to avoid the inadvertent generation of cavitation bubbles during the displacement of the pattern in the cutting plane . 2.5.3.5. Remarks

We have described how to place the points of impact of a multipoint laser beam, so that the generated bubbles have a uniform and regular arrangement on the cutting surface of the fabric. Among an infinity of non-regular arrangements, which can also be used, we have shown that to obtain a regular equilateral triangle arrangement, there were two types of preferred motifs and that to obtain a regular square arrangement, there was a preferred pattern. . For all preferred matrices, the spacings and angles between each point of the matrix were calculated.

Of course, the invention also relates to any type of pattern whose points of impact are sufficiently spaced from each other to avoid interference and whose movement allows to obtain by projection a relatively homogeneous coverage of the surface to be cut, even without regular repetition of a geometric matrix, even if the matrices presented give better results. The disadvantage of this type of pattern form is the introduction of a "priming zone" 102 on the periphery of a regular zone 103. In this priming zone 102, the cutout is incomplete, as illustrated in FIG. Although the size of this priming zone 102 is very small compared to the overall size of the cut (less than 0.5% of a comedic hood diameter of 8 mm for the examples presented), this zone of FIG. Priming 102 should preferably be as short as possible. 3. Principle of operation

The operating principle of the cutting apparatus illustrated in FIG. 1 will now be described with reference to the destruction of a lens in the context of a cataract operation. It is obvious that the present invention is not limited to the operation of a cataract.

In a first step, the control unit 6: - transmits to the formatting system 3 a first phase mask associated with a first processing pattern (for example the pattern shown in FIG. X), transmits a control signal the optical focusing system 5 for moving the plane of focus at a first deep cutting plane in the eye, activates the movement of the scanning optical scanner 4 to an initial cutting position. As the scanning is done in X, Y, the scanner is equipped with a mirror, X, which allows scanning along each segment of the path of movement of the pattern, and another mirror Y, which once allows a completed segment, to change segment. The mirrors X and Y therefore function alternately one and the other. When the focusing system 5 and the optical scanner 4 are in position and the phase mask is loaded in the shaping system 3, the control unit 6 activates the femtosecond laser 1. This generates a beam L.A.S.E.R. 11 which passes through the shaping system 3. The shaping system 3 modulates the phase of the beam L.A.S.E.R. The beam L.A.S.E.R. modulated in phase 31 leaves the formatting system 3 and enters the optical scanner 4 which deflects the beam of L.A.S.E.R. modulated 31. The beam LA.S.E.R. Modulated and deflected 41 enters the focusing optical system 5 which focuses the beam in the first plane of cutting.

Each point of impact 81 of the pattern 8 produces a cavitation bubble. The femtosecond laser 1 continues to emit other pulses in the form of LA.S.E.R beam. at a specified rate. Between each pulse the mirror X has rotated by a certain angle, which has the effect of moving the pattern 8 and producing new cavitation bubbles offset from the previous ones, until forming a line. Thus, a first plurality of cavitation bubbles constituting a line is formed in the cutting plane, these bubbles being arranged according to the cutting pattern 8.

Once this plurality of bubbles forming a complete line, the control unit 6 deactivates the source L.A.S.E.R. 1, controls the stopping of the pivoting of the mirror X and controls the pivoting of the mirror Y of the optical scanner 4 to the next cutting position according to the scan step of the optical scanner 4, and then commands the restart of the pivoting of the mirror. mirror X in the opposite direction. When the optical scanner 4 is in position and the mirror X has reached its constant target speed, the control unit 6 activates again the femtosecond laser 1. The beam L.A.S.E.R. 11 passes through the shaping system 3, the optical scanner 4 and the optical focusing system 5. A second sequence of a plurality of cavitation bubbles is formed in the first cutting plane forming a new line parallel to the previous one and juxtaposed.

These operations are repeated throughout the first cutting plane.

When the optical scanner 4 has scanned the entire surface of the first cutting plane, a first cutting area (the shape and dimensions of which are controlled by the control unit 6) is generated. The control unit 6 deactivates the femtosecond laser 1 and controls: translational displacement of the lens (s) of the optical focusing system 5 to move the focusing plane 21 in a second cutting plane; rotational movement of the mirror (s) of the optical scanner 4 to an initial cutting position of the second cutting plane, the possible loading by the shaping system 3 of another phase mask to modify the arrangement and / or the size of the impact points of the pattern, etc. The control unit 6 repeats the piloting operations of the femtosecond laser 1, the shaping system 3, the scanning optical scanner 4 and the focusing system 5 in the second cutting plane, and more generally in the planes of FIG. successive cutting. At the end of these different steps, a stack of cutting planes corresponding to the volume to be destroyed is obtained.

Thus, the invention makes it possible to have an effective cutting tool. The dimensions of the impact points of the pattern being substantially equal (the shape, position and diameter of each spot are dynamically controlled by the phase mask calculated and displayed on the SLM and which can correct the irregularities), the cavitation bubbles which dilated the cut organic tissue will be of substantially equal size. This makes it possible to improve the quality of the result obtained, with a homogeneous cutting plane, in which the residual tissue bridges all have approximately the same size and which allow dissection by the practitioner of an acceptable quality in view of the importance of the quality of the surface condition of the cut fabric when it is for example a cornea. The invention has been described for corneal cutting operations in the field of ophthalmic surgery, but it is obvious that it can be used for other types of operation in ophthalmic surgery without departing from the scope of the invention. 'invention. For example, the invention finds application in corneal refractive surgery, such as the treatment of ametropia, including myopia, hyperopia, astigmatism, in the treatment of loss of accommodation, including presbyopia. The invention also finds application in the treatment of cataract with incision of the cornea, cutting of the anterior capsule of the lens, and fragmentation of the lens. Finally, more generally, the invention relates to all clinical or experimental applications on the cornea or lens of a human or animal eye. Even more generally, the invention relates to the broad field of L. A.S.E.R. and finds an advantageous application when it comes to cutting and more particularly vaporize human or animal soft tissues with high water content.

The reader will have understood that many modifications can be made to the invention described above without physically going out of the new teachings and advantages described herein.

For example, in the various embodiments described above, the optical focusing system disposed downstream of the scanning optical scanner was described as comprising a single module allowing: on the one hand to focus the beam L.A.S.E.R. modulated and deflected, and secondly to move the plane of focus in different cutting planes.

In a variant, the optical focusing system may be composed of two distinct modules each providing one of these functions: a first module, called a "deep positioning module", arranged upstream of the scanning optical scanner and making it possible to move the plane of focus in different cutting planes. a second module, called a "concentrator module", placed downstream of the scanning optical scanner and making it possible to focus the beam L.A.S.E.R. modulated and deviated.

Therefore, all such modifications are intended to be incorporated within the scope of the appended claims.

Claims (9)

claims 1. Apparatus for cutting a human or animal tissue, such as a cornea, or a lens, said apparatus including a beam treatment device L.A.S.E.R. generated by a femtosecond laser, and disposed downstream of said femtosecond laser, characterized in that the processing device comprises: - a shaping system (3) positioned on the path of said beam, for modulating the phase of the wavefront of the LASER beam so as to obtain a beam L.A.S.E.R. phase modulated according to a modulation instruction calculated to distribute the energy of the beam L.A.S.E.R. at least two impact points (81) forming a pattern (8) in its focal plane (21) corresponding to a cutting plane, each impact point making a cut, - an optical scan scanner (4) arranged downstream of the shaping system for moving the pattern in the cutting plane at a plurality of positions (43) in a direction of movement (D), a control unit including a processor programmed to enable control of the femtosecond laser, of the shaping system and the scanning optical scanner to tilt the pattern with respect to the direction of movement so that at least two pattern impact points are spaced apart: - from a non-zero distance in accordance with a first axis parallel to the direction of movement on the one hand, and - a non-zero distance along a second axis perpendicular to the direction of movement on the other hand. The cutting apparatus according to claim 1, wherein the pattern comprises at least two adjacent (including three) adjacent impact points extending along a line of the pattern, the angle between said pattern line and the direction. displacement of between 10 and 80 °, preferably between 15 ° and 40 °, and even more preferably between 19 ° and 30 °. Cutting apparatus according to any one of the preceding claims, wherein the pattern comprises: - a first set of at least two (including three) impact points arranged along a first line of the pattern, and - A second set of at least two (including three) other impact points arranged along a second line of the pattern parallel to the first line. The cutting apparatus according to claim 3, wherein the pattern further comprises at least one other set of impact points disposed along at least one other line of the pattern, parallel to the first and second lines. 5. Cutting apparatus according to any one of claims 3 or 4, wherein the impact points of the second set are offset by a non-zero distance from the impact points of the first set. 6. Cutting apparatus according to any one of claims 3 or 4, wherein each point of impact of the second set is aligned with a respective point of impact of the first set along a line perpendicular to the direction of travel. 7. Cutting apparatus according to any one of claims 1 to 6, wherein the distance between two adjacent impact points of the pattern is greater than 5pm, preferably greater than 10pm and even more preferably between 10 and 15pm. 8. Cutting apparatus according to any one of claims 1 to 7, wherein the pattern is inscribed in a surface whose ratio between the length and the width is between 1 and 4, preferably between 1 and 2, and even more preferably between 1 and 1.5. Cutting apparatus according to any one of the preceding claims, wherein the pattern comprises a central impact point positioned at the centroid of the pattern.